“Developments in Ukraine and the situation with the U.S. bombings in Syria and Iraq are on investors’ minds,” he added.

The European Union (EU) will hold fresh talks with Russia and Ukraine later Friday in Berlin to settle their ongoing dispute over gas deliveries.

Europe gets more than 30 percent of its gas from Russia, with half of that transiting through Ukraine.

In June, Moscow cut off supplies for Kiev owing to a bitter price dispute that took place against the backdrop of an armed insurgency by pro-Kremlin rebels in east Ukraine.

Gas is flowing as normal through Ukraine into the EU, but Russia has warned there is a high risk of disruption of deliveries to Europe this winter as international tensions remain high over the Ukraine crisis.

Crude investors are also keeping watch as the U.S. and its Arab allies turn up the heat on the Islamic State of Iraq and Syria group, striking oil facilities funding their uprising.

ISIS has overrun large swathes of Iraq and Syria and declared a “caliphate” in those areas.

The sweeping jihadist offensive began on June 9, preventing Baghdad from exporting oil via a pipeline to Turkey and by road to Jordan.

A three-year civil war in Syria between the government and insurgents including IS has seen its crude exports dip to around 25,000 barrels a day from 400,000 in 2010.